Current electric vehicles often use power batteries with large capacities, which may improve the driving range of electric vehicles. However, a long charging time is required when recharging the battery. Although a charging station can charge the power battery quickly, it still has disadvantages such as high cost and requires a relatively large work area. Thus it is very difficult to increase the density of the charging stations. Besides, due to the limited space in an electric vehicle, the in-vehicle charger is limited by the available space thereof and is often unable to meet the requirement of high charging power.
In addition, to charge a conventional electric vehicle, a dedicated charging pile is required and different circuits need to be constructed for a charging system to accommodate different connection modes of the external power grid. This increases hardware costs. Moreover, the current three-phase charging system of the electric vehicle only accommodates the star—type connection mode, which reduces the usability of the charging system.